Start playing right away though, because it's not yours to keep.
We've seen a few free games come and go as of late, but most of them you can put on the back-burner. That copy of The Darkness 2 we posted about last week? Wait until the dead of winter, if you like.
So while, yes, This War of Mine is presently free on Steam, it's actually a more generous spin on those occasional 'play multiplayer over the weekend' things that sometimes crop up. There are still four days remaining, though, so if the thought on a scavenging civilian's war experience sounds like an enticing twist on typical videogame formula, you may want to dig in right away.
Appropriately, it's also on deep sale, just in case you get uncontrollably hooked.